HONG KONG, China --Health officials in Hong Kong battling the deadly SARS virus say they are increasingly concerned at the number of relatively young and apparently otherwise healthy people falling victim to the disease.

The remarks came as Chinese Premier Wen Jiabao said the SARS outbreak in China was "grave" -- a departure from assurances the illness was under control in the nation where it is suspected to have emerged.

But hope has been raised by researchers in Canada, who said they had uncovered the genetic code for the SARS virus. The breakthrough could lead to tests for the illness and a possible cure. (Genome mapped)

The global death toll from severe acute respiratory syndrome (SARS) has now topped 130, including four new fatalities in China announced Monday by the World Health Organization (WHO).

As concerns rise over the mystery disease, for which there is still no cure, Hong Kong officials say they are looking at why six people aged between 35 and 52 died in the last few days.

Most of the other deaths in Hong Kong have been of elderly patients or those suffering from chronic pre-existing conditions such as heart or kidney disease.

On Monday, Hong Kong officials reported seven more deaths from the virus and 40 new cases -- bringing to 47 the number of deaths in the city.

Hong Kong's Department of Health and Hospital Authority said since the outbreak began March 12, 229 patients have recovered from the ailment. Six of them were discharged from hospitals Monday.

Hong Kong doctors have started prescribing heavier doses of medicine during the early stages of SARS. However, one expert voiced concern to The Associated Press that the virus may have mutated.

The World Health Organization and the Centers for Disease Control say the disease is caused by a newly recognized coronavirus -- the same virus family that causes the common cold.

The CDC said its accounting of the complete genome of the virus would be available Monday.

Working with the code

Over the weekend scientists in Canada said they had uncovered the genetic code for the SARS virus, raising hopes the breakthrough could pave the way to a quick test for the illness and a possible vaccine.

Caroline Astell, projects leader at the Genome Science Centre in British Columbia, said the code was an important step towards finding an effective treatment to the virus and helping to understand why SARS is so deadly.

More than 3,000 people around the world have been infected with the virus -- the majority of the cases in Asia and Canada.

Most sufferers recover with prompt medical attention, with about 4 percent of those infected dying.

Nevertheless, the WHO is not letting its guard down one month after issuing its first alert on the disease, warning that SARS could become a global epidemic.

"If the SARS maintains its present pathogenicity and transmissibility, SARS could become the first severe new disease of the 21st century with global epidemic potential," David Heymann, the agency's executive director of communicable diseases, wrote on the WHO Web site over the weekend.

Alarm over the spread of SARS has hit Asian economies hard, particularly businesses related to the travel and tourism industries.

Meanwhile, the Association of Asia Pacific Airlines has called on governments not to act in "an arbitrary or counterproductive fashion" in dealing with the spread of SARS.

In a statement Monday the association's director-general said the virus has put regional airlines in their "worst ever" situation.

The statement added that arbitrary blanket bans and other "unhelpful measures" would only lead to retaliation, confusion and further difficulties for an already troubled industry.

In other developments:

• After a near blackout on SARS coverage, China is orchestrating a media blitz to convince its citizens to adopt healthier lifestyles, warning against smoking and drinking, urging scrubbing of hands after cleaning noses, and advising keeping surgical face masks on hand just in case.

• WHO officials say while there are signs the epidemic is being contained elsewhere in the world, concerns remain about the ability of infected areas in China to recognize and control the illness. Recently cases have been reported in the poor northwestern province of Inner Mongolia, thousands of kilometers from Guangdong, where the virus is thought to have originated.

• Singapore's primary schools re-opened Monday after being closed for more than two weeks in a bid to halt the spread of SARS. Asked if he believed the virus was under control, Singapore Health Minister Lim Hng Kian said authorities were "in this for the long haul," Reuters reported.

• Japan's Ministry of Health announced Monday four of the cases it had previously reported to WHO turned out not to be SARS. The ministry also said it has another suspected case which is being investigated and has not yet been reported to WHO.

• Cruise ship operator Star Cruises Ltd. said on Monday two crew members who were admitted to hospital last week as possible SARS cases have recovered.